My experience watching this video:

Fireworks don't work underwater.

Huh, fireworks might work underwater.

Wait, why isn't that firework going anywhere underwater?

That firework is going to kill that dude from underwater!

Whew, close call.

Wow, a firework detonated underwater.

That firework could have blown that dude's hand off even from underwater.

Poor fish.

Poor underwater fish.

I wonder if there are more videos of fireworks underwater.

*Googles.*

Yes, there are more videos of fireworks underwater.